diff --git a/include/assert_macros.h b/include/assert_macros.h
index 065f8d1..0b33206 100644
--- a/include/assert_macros.h
+++ b/include/assert_macros.h
@@ -6,8 +6,21 @@
 #undef call_assert_describe
 #undef call_assert_diagnose
 
-#ifdef DEBUG
-# define call_assert(assertion) call assert(assertion, "No description provided (see file " // __FILE__ // ", line " // string(__LINE__) // ")")
+! Check user-provided flags to decide whether assertions are enabled
+#if defined(DEBUG) && defined(NDEBUG)
+# error Please define at most one of DEBUG or NDEBUG
+#endif
+
+! Deal with Fortran's stringification debacle:
+! https://gcc.gnu.org/legacy-ml/fortran/2009-06/msg00131.html
+#ifdef __GFORTRAN__
+#define STRINGIFY(x) "x"
+#else
+#define STRINGIFY(x) #x
+#endif
+
+#if defined(DEBUG)
+# define call_assert(assertion) call assert(assertion, STRINGIFY(assertion) // " in file " // __FILE__ // ", line " // string(__LINE__) // ")")
 # define call_assert_describe(assertion, description) call assert(assertion, description // " in file " // __FILE__ // ", line " // string(__LINE__) // ": " )
 # define call_assert_diagnose(assertion, description, diagnostic_data) call assert(assertion, "file " // __FILE__ // ", line " // string(__LINE__) // ": " // description, diagnostic_data)
 #else
diff --git a/test/test-assert-macro.F90 b/test/test-assert-macro.F90
index 770df48..dda15a8 100644
--- a/test/test-assert-macro.F90
+++ b/test/test-assert-macro.F90
@@ -53,6 +53,10 @@ program test_assert_macros
 
   end block
 
+  call_assert(100 == 200)
+  ! call_assert(100 + 200 + 1 + 1 + 1 + 1 + 1 == 2 + 2 + 2 + 2 + 3 + 1)
+  call_assert_diagnose(1==2, "up is down", diagnostic_data=1)
+
 #undef DEBUG
 #include "assert_macros.h"
   call_assert_describe(.false., "")